Field of the Invention
The present invention relates to a vehicle braking system.
Description of the Related Art
Japanese Patent Laid-open No. 2009-227023 (which is hereinafter referred to as JP2009-227023A) discloses the following technique. According to the disclosed technique, at the start of operation of a yaw-moment control device, a slave cylinder is temporarily operated, a brake pressure generated in the slave cylinder is added to a brake pressure generated by the yaw-moment control device, and the sum of the brake pressures is outputted to wheel cylinders. The object of the above technique is to supplement deficiency in the initial responsiveness of the brake pressure generated by the yaw-moment control device with the initial responsiveness of the brake pressure in the slave cylinder and generate a brake pressure having high initial responsiveness.
In addition, according to the technique disclosed in Japanese Patent Laid-open No. 2005-153716 (which is hereinafter referred to as JP2005-153716A), the yaw moment of a vehicle is feedforward controlled and feedback controlled according to the steering angle and the like of the vehicle.
The technique disclosed in JP2009-227023A is intended to improve the initial responsiveness of the yaw-moment control by operating the slave cylinder in an initial stage of the yaw-moment control and increasing the hydraulic brake pressure.
However, in the case where the slave cylinder is operated as above at the start of the yaw-moment control in which braking force begins to be applied in advance of occurrence of a disturbance in the vehicle behavior by feedforward control or the like, the accuracy of the yaw-moment control is lowered. (See JP2005-153716A and the like for the yaw-moment control as above.) That is, in the yaw-moment control as disclosed in JP2005-153716A and the like, the yaw moment control is performed by generating a relatively small braking force. Therefore, when the braking force generated in the slave cylinder is added to the small braking force as above, it is difficult to accurately control the brake pressure to be equal to a target brake pressure.